1. Field of the Invention
This invention relates to a method of driving a plasma display panel, and more particularly to an address driving method of a plasma display panel that permits a stable high-speed addressing.
2. Description of the Related Art
Generally, a plasma display panel (POP) radiates a fluorescent body by an ultraviolet with a wavelength of 147 nm generated during a discharge of He+Xe or Ne+Xe gas to thereby display a picture. Such a PDP is easy to be made into a thin-film and large-dimension type. Moreover, the PDP provides a very improved picture quality owing to a recent technical development. Such a PDP typically includes a surface-discharge alternating current (AC) type PDP that has three electrodes as shown in FIG. 1 and is driven with an alternating current voltage.
FIG. 1 is a perspective view of a discharge cell of a conventional three-electrode, AC-type PDP. Referring to FIG. 1, the discharge cell includes an upper substrate 10 provided with a sustaining electrode pair 12 and 14, and a lower substrate 20 provided with an address electrode 22. The upper substrate 10 and the lower substrate 20 are spaced, in parallel to each other, with having a barrier rib 26 therebetween. A mixture gas such as Nexe2x80x94Xe or Hexe2x80x94Xe, etc. is injected into a discharge space defined by the upper substrate 10 and the lower substrate 20 and the barrier rib 26. Any one electrode 12 of the sustaining electrode pair 12 and 14 is used as a scanning/sustaining electrode that responds to a scanning pulse applied in the address interval to cause an opposite discharge along with the address electrode 22, and responds to a sustaining pulse applied in the sustaining interval to cause a surface discharge along with the adjacent sustaining electrode 14. The sustaining electrodes 14 adjacent to the sustaining electrode 12 used as the scanning/sustaining electrode are used as a common sustaining electrode to which a sustaining pulse is applied commonly. On an upper substrate 10 provided with the sustaining electrode pair 12 and 14, an upper dielectric layer 16 and a protective film 18 are disposed. The upper dielectric layer 16 is responsible for limiting a plasma discharge current as well as accumulating a wall charge during the discharge. The protective film 18 prevents a damage of the upper dielectric layer 16 caused by a sputtering generated during the plasma discharge and improves an emission efficiency of secondary electrons. This protective film 18 is usually made from MgO. The address electrode 22 crosses the sustaining electrode pair 12 and 14 and is supplied with a data signal for selecting cell to be displayed. A lower dielectric layer 24 is formed on the lower substrate 20 provided with the address electrode 22. The barrier ribs 26 for dividing the discharge space are extended perpendicularly on the lower dielectric layer 24. The surfaces of the lower dielectric layer 24 and the barrier rib 26 is coated with a fluorescent material 28 excited by a vacuum ultraviolet ray to generate a red, green or blue visible light.
The PDP discharge cell having the structure as described above sustains a discharge by a surface discharge between the sustaining electrode pair 12 and 14 after being selected by an opposite discharge between the address electrode 22 and the scanning/sustaining electrode 12. The fluorescent material 28 is radiated by an ultraviolet ray generated during the sustaining discharge to emit a visible light into the exterior of the cell. In this case, a discharge sustaining interval, that is, a sustaining discharge frequency of the cell is controlled to realize a gray scale required for an image display.
An arrangement of the entire electrode lines and discharge cells of the AC surface-discharge PDP is as shown in FIG. 2. In FIG. 2, the discharge cell 30 is positioned at each intersection among m address electrode lines X1 to Xm, n scanning/sustaining electrode lines Y1 to Yn and n common sustaining electrode lines Z1 to Zn. The address electrode lines X1 to Xm are divided into odd-numbered lines and even numbered lines to be individually driven at the upper and lower portion thereof, respectively. The scanning/sustaining electrode lines Y1 to Yn are individually driven while the common sustaining electrode lines Z1 to Zn are commonly driven.
Such a PDP driving method typically includes a sub-field driving method in which the address interval and the discharge sustaining interval are separated. In the sub-field driving method as shown in FIG. 3, one frame 1F is divided into n bits for example, 8 sub-fields SF1 to SF8 corresponding to each bit of an 8-bit image data, and each sub-field SF1 to SF8 is again divided into a reset interval RPD, an address interval APP and a discharge sustaining interval SPD. The reset interval RPD is an interval for initializing the discharge cell, the address interval APD is an interval for generating a selective address discharge in accordance with a logical value of a video data, and the sustaining interval SPD is an interval for allowing a discharge to be sustained at the discharge cell 12 in which the address discharge has been generated. The reset interval RPO and the address interval APD are equally allocated in each sub-field interval. A weighting value with a ratio of 20:21:22: . . . :2nxe2x88x921, i.e., 1:2:4:8:16:32:64:128 is given to the discharge sustaining interval SPD to express a gray scale by a combination of the discharge sustaining intervals SPD.
FIG. 3 is waveform diagrams of driving signals applied to the PDP shown in FIG. 2 in a certain one sub-field interval SFi. In the reset interval RPD, a priming pulse Pp is commonly applied to the scanning/sustaining electrode lines Y1 to Yn and the common sustaining electrode lines Z1 to Zn. By this priming pulse Pp, a reset discharge is generated between each common sustaining electrode and each scanning/sustaining electrode of the entire discharge cells 30 to initialize the discharge cells 30. By the reset discharge, a large amount of wall charges are formed at the common sustaining electrode and the scanning/sustaining electrode of each discharge cell 30.
Subsequently, a self-erasure discharge is generated at the discharge cells by the large amount of wall charges to eliminate the wall charges and leave a small amount of charged particles. These small amount of charged particles help an address discharge in the following address interval. In the address interval APD, a scanning voltage pulse SCp is applied line-sequentially to the scanning/sustaining electrode lines Y1 to Yn. At the same time, a data pulse Dp according to a logical value of a data is applied to the address electrode lines X1 to Xm. Thus, an address discharge is generated at discharge cells to which the scanning voltage pulse SCp and the data pulse Dp are simultaneously applied. Wall charges are formed at the discharge cells in which the address discharge has been generated. During this address interval, a desired constant voltage is applied to the common sustaining electrode lines Z1 to Zn to prevent a discharge between each address electrode line and each common sustaining electrode line. In the sustaining interval SPD, a sustaining pulse Sp is alternately applied to the first to mth scanning/sustaining electrode lines Y1 to Ym and the common sustaining electrode lines Z1 to Zn. Accordingly, a sustaining discharge is generated continuously only at the discharge cells formed with the wall charges by said address discharge to emit a visible light. Then, in a separate erasure interval EPD, an erasing pulse Ep is applied to the common sustaining electrode lines Z1 to Zn to interrupt the sustained discharge.
In the conventional AC, surface-discharge PDP driven as described above, there has been used a scheme of lengthening a pulse width Td of address drive pulses Dp and SCp into more than 2.5 xcexcs or enlarging a voltage level of the address drive pulses Dp and SCp in order to obtain a stable discharge characteristic. If a voltage level of the address drive pulse Dp and SCp are lowered, then a discharge intensity and a produced amount of charged particles are reduced. If the address drive pulses Dp and SCp is shortened into a pulse width T1 at such a low voltage level state, then a mis-discharge or an erroneous discharge may be generated due to a discharge delay phenomenon which is an inherent characteristic of the PDP. Such an unstable address discharge problem can be solved by lengthening the pulse width T1 of the drive pulses Dp and SCp.
However, when the pulse width T1 of the address drive pulses Dp and SCp is set to have a large value of more than 2.5 xcexcs, a ratio occupied by the sustaining interval SPD dominating a brightness of a real picture in a state in which a period of one frame 1F has been fixed to 16.67 ms is reduced to less than 30% to deteriorate the brightness. Also, a recent PDP driving method has increased the number of sub-fields in one frame 1F from 8 sub-fields in the prior art into 10 to 12 sub-fields so as to reduce a contour noise which is an inherent picture quality deterioration phenomenon. If the number of sub-fields increases during the fixed one frame interval, a sustaining interval of each sub-field is shortened to thereby largely deteriorate a picture brightness. Furthermore, in the case of a high-resolution POP having a lot of scanning lines, an address interval is more lengthened and thus a sustaining interval is shortened to that extent, thereby making a picture display impossible,
In order to overcome such a problem, there has been implemented various method for reducing an address interval using a high-speed addressing. One example of these methods is to divide scanning lines into upper and lower lines to drive them. In this scanning line division driving system, scanning lines are divided into the upper and lower lines to drive the upper scanning lines and the lower scanning lines simultaneously with two different scanning drivers. Accordingly, the address interval is shortened into xc2xd and thus the sustaining interval is sufficiently assured, thereby preventing a brightness deterioration of a picture. However, the scanning line division driving system has a drawback in that, since the number of scanning and address driver integrated circuits (IC""s) is increased to two times, a manufacturing cost of the PDP rises.
Another method for a high-speed addressing is to cause a auxiliary discharge during the address discharge to short an address interval. In order to generate the auxiliary discharge, a discharge cell 34 of a PDP as shown in FIG. 5 further includes a auxiliary electrode 32 formed, in parallel to an address electrode 22 on a lower substrate 20 in comparison to the discharge cell 30 shown in FIG. 1. In such a discharge cell 34, the address electrode 22 and a scanning/sustaining electrode 12 generate an address discharge and, at the same time, the auxiliary electrode 32 causes a auxiliary discharge along with the address electrode 22. In this case, a stable address discharge is generated with the aid of the auxiliary discharge even when a width of a voltage pulse for causing an address discharge is reduced.
FIG. 6 shows an entire electrode arrangement of a PDP in which said discharge cells 34 are arranged in a matrix type. In the PDP shown in FIG. 6, n scanning/sustaining electrode lines Y1 to Yn and common sustaining electrode lines Z1 to Zn are alternately arranged, and m address electrode lines X1 to Xm and m auxiliary electrode lines A1 to Am are arranged in such a manner to cross the scanning/sustaining electrode lines Y1 to Yn and the common sustaining electrode lines Z1 to Zn.
FIG. 7 is waveform diagrams of signals for driving the PDP shown in FIG. 6. In a reset interval RPD, a priming pulse Pp is commonly applied to the scanning/sustaining electrode lines Y1 to Yn and the common sustaining electrode lines Z1 to Zn. By this priming pulse Pp, a reset discharge is generated at all of the discharge cells 34 to initialize them. In an address interval APD, a negative(xe2x88x92) scanning voltage pulse SCp is line-sequentially applied to the scanning/sustaining electrode lines Y1 to Yn. At the same time, a positive(+) data pulse Dp according to a logical value of a data is applied to the address electrode lines X1 to Xm. Also, whenever the data pulse Dp is applied, a negative(xe2x88x92) auxiliary pulse Ap is applied to the auxiliary electrode lines A1 to Am. Accordingly, at discharge cells to which a positive(+) data pulse Dp is applied, an address discharge is generated between the address electrode and the scanning/sustaining electrode and an auxiliary discharge is further generated between the address electrode and the auxiliary electrode. In this case, sufficient priming charged particles are produced at the discharge space by virtue of the auxiliary discharge, a pulse width Td of a drive pulse for an address discharge, that is, the data pulse DP and the scanning pulse SCp can be shortened into Less than 1 xcexcs. As a width of a driving pulse for an address discharge is shortened, an address interval APD in each sub-field is largely shortened into less then xc2xd in comparison to the prior art. Wall charges are produced at the discharge cells in which an address discharge has been generated. During this address interval APD, a desired constant voltage Vr is applied to the common sustaining electrode lines Z1 to Zn to prevent a discharge from being generated between each common sustaining electrode line and each address electrode line. In a sustaining interval SPD, a sustaining discharge is continuously generated only at the discharge cells in which wall charges are produced by said address discharge with the aid of a sustaining pulse SUSp applied alternately to the scanning/sustaining electrode lines Y1 and Yn and the common sustaining electrode lines Z1 to Zn. Then, in a separate erasure interval EPD, an erasing pulse Ep is applied to the common sustaining electrode lines Z1 to Zn to interrupt the sustained discharge.
However, the conventional PDP driving method employing the auxiliary discharge has a problem in that it has a high possibility for generating an erroneous discharge between the address electrode and the auxiliary electrode. This is caused by a fact that an auxiliary pulse having the same polarity as a scanning pulse, that is, a negative polarity is applied to the auxiliary electrode for the sake of an auxiliary discharge. More specifically, the conventional PDP driving method has a problem in that, if a positive(+) data pulse Dp is applied to the data electrode 22 and a negative(xe2x88x92) auxiliary pulse Ap is applied to the auxiliary electrode 32 even though a negative scanning pulse is not applied to the scanning/sustaining electrode 12, then an erroneous discharge may be generated at the discharge cells in which a discharge must not be generated due to a voltage difference between the data pulse Dp and the auxiliary pulse Ap. Furthermore, since it is general that the negative(xe2x88x92) voltage has slightly more difficulty than the positive(+) voltage in controlling them, a voltage level control of the negative(xe2x88x92) auxiliary pulse Ap applied to the auxiliary electrode 32 becomes difficult to more increase a possibility of the above-mentioned erroneous discharge.
Accordingly, it is an object of the present invention to provide an address driving method of a plasma display panel (PDP) that permits a stable high-speed addressing,
In order to achieve these and other objects of the invention, an address driving method comprising the steps of: applying a data pulse to an address electrode and applying a scanning pulse to a scanning electrode, to thereby generating an address discharge in the selected cell; and applying an auxiliary pulse to an auxiliary electrode parallel to the address electrode, to thereby generating an auxiliary discharge.